I buy two sorts of prawns.
One sort is from the chilled section and ready cooked, I use them in things like prawn cocktail, mixed in with a sauce. I would never use them in a dish which needs cooking.
The other sort are giant raw ones, not in the shell, and frozen. I buy them from Costco and use them, defrosted, in any dish I’m cooking which calls for prawns. Once they’re defrosted they only take a few minutes if frying them, or at the most ten or twelve minutes in the oven stirred into the recipe I’m making. I would NEVER boil them.